Devices that are used to separate egg yolks from egg whites are well known and usually operate by having a receptacle for retaining the yolk and apertures of varying design for straining the egg white from the yolk. They are usually available in the form of a handheld implement. Several of those known in the art have a dual functionality such as lemon squeezers and the like.
On such device can be found in U.S. Pat. No. 1,492,385, issued Apr. 29, 1924 to Moritz. The device is a cup that has a handle and has located in its center/bottom, separators for squeezing lemons. The separator has an opening in the dead center of the cup to pass the egg whites through into a receiver bowl.
A similar device can be found in U.S. Pat. No. 2,212,328, Issued Aug. 20, 1940 to Scurlock.
There is disclosed in U.S. Pat. No. 4,463,666, that issued Aug. 7, 1984 to Papp an egg separator that has a receptacle with a bottom wall that slopes toward the center where there is a tubular hollow upright provided with circumferentially spaced vertical openings leading to a center discharge hole for the egg whites, the yolks being held back at the openings. It does not specifically identify what sort of device prevents the yolk from descending into the receiver.
A similar device can be found in U.S. Pat. No. 5,438,919, that issued on Aug. 8, 1995 to Idowu. The device is rather complicated and it consists of a housing having an inner chamber and an outer chamber. It has a lid member detachably coupled to an upper edge of the housing. The lid includes an annular member positioned above the inner chamber and a plurality of slots disposed adjacent to the annular member communicating with the outer chamber. Ther is also a funnel attached to the lid. The annular member is sized for retaining the yolk and for causing the egg white to overflow the annular member with the slots allowing the egg white to flow downwardly into the outer chamber. A means is also provided for channeling the separated yolk into the opposite chamber.
There is disclosed in U.S. Pat. No. 6,303,915 that issued on Oct. 16, 2001 to Young et al, a device for separating and cooking egg whites. A heat resistant bowl includes a bottom portion and a wall portion, a lid for removably engaging the wall portion of the bowl in a snug fit, and a separator for separating liquid egg whites from eggs, the separator being connected to the lid whereupon the egg whites are cooked in the bowl by subjecting the bowl to microwaves.
U.S. Design Pat. No. 307,527 discloses an egg separator that is a small pan with elongated slits in the bottom.
U.S. Pat. No. 6,095,038 that issued on Aug. 1, 2000 to Cerro deals with an egg white and yolk separator that has multiple concavities that have elongated slits in the bottom of the concavities.
U.S. Pat. No. 6,915,735 that issued on Jul. 12, 2005 to So, deals with an egg yolk separator that includes a strainer having a portion for retaining an egg yolk and aperture for straining egg white. A pair of arms extends in opposite directions from the strainer for resting on opposite sides of an opening of a vessel. One of the arms is extendable and retractable in length such that overall length of the separator is adjustable to suit the width of the opening of the vessel. The strainer has elongated lateral slits near the middle of the strainer for allowing egg whites to sift through, however, this device also has a centrally located aperture in the bottom of the strainer.